Process for producing fatty alcohols from fatty acid methyl ester

Abstract

Subject-matter of the invention is a process for producing fatty alcohols by catalytic hydrogenation of fatty acid methyl ester (FAME), in which the FAME initially is hydrogenated to fatty alcohol (FA). The fractions of non-converted FAME remaining in the hydrogenation product are converted to wax ester and methanol in a succeeding transesterification step with FA. According to the invention, catalysts on the basis of magnesium oxide or hydrotalcite are used. After separating the methanol and the FA as target product, a stream enriched in wax ester is recirculated to the hydrogenation reactor.

The invention claimed is: 
     
       1. A process for obtaining fatty alcohols (FA) from fatty acid methyl ester (FAME), the process comprising the steps of:
 (a) supplying a feed stream containing fatty acid methyl ester to a hydrogenation stage, conversion of the feed stream in the presence of hydrogen under hydrogenation conditions on a bed of solid, granular hydrogenation catalyst, discharging a first material stream containing fatty alcohol, methanol and non-converted FAME; 
 (b) supplying the first material stream to a distillation stage, separating the methanol as top product of the distillation, and discharging the bottom product of the distillation as second material stream comprising fatty alcohol and FAME; 
 (c) supplying the second material stream to a transesterification reactor filled with a bed of solid, granular catalyst, transesterification of the second material stream under transesterification conditions to a third material stream comprising fatty alcohol and wax ester (WE) in counterflow with an inert gas stream as stripping gas stream, wherein the methanol produced during the transesterification is separated with the stripping gas as top product and the third material stream comprising fatty alcohol and wax ester is discharged; 
 (d) supplying the third material stream to a separation stage operating by a thermal separation process, separating a fourth material stream enriched in wax ester, discharging a fifth material stream depleted of wax ester and enriched in fatty alcohol as fatty alcohol product stream; and 
 (e) recirculating the fourth material stream enriched in wax ester to the hydrogenation stage (a), 
 wherein in process step (c) a transesterification catalyst on the basis of magnesium oxide or hydrotalcite is used. 
 
     
     
       2. The process according to  claim 1 , wherein the separation stage in process step (d) is designed as distillation stage, wherein the fourth material stream enriched in wax ester is obtained as bottom product and the fifth material stream depleted of wax ester and enriched in fatty alcohol is obtained as top product. 
     
     
       3. The process according to  claim 1 , wherein the separation stage in process step (d) is designed as winterization stage and the fourth material stream enriched in wax ester, which is deposited under winterization conditions, is separated by means of a mechanical separation process. 
     
     
       4. The process according to  claim 3 , wherein the mechanical separation process is selected from the group consisting of sedimentation, decantation, filtration, and combinations thereof.